The present invention relates to an arrangement for roller suspension at a printer of a kind usable for printing and feeding of labels, tickets, receipts, luggage tags, etc. More particularly, an arrangement with overhung suspension of the rollers is intended. The invention comprises a design that contains few parts, resulting in lower costs for production assembly. With a low cost solution the design permits the feeding of paper to run perpendicularly to the chassis, and the design is furthermore open and easily assessable, simplifying service as well as usage.
A plurality of different printers are available on the market, intended for printing of a printing material in the form of labels mounted on a paper slip, or for example for printing of paper tickets. An often used design is a printer with through print and feed rollers, which rollers are anchored in both roller ends at the chassis of the printer. One of the problems with these printers is that they contain many parts, often many moving parts, resulting in a design were many thing can brake. A design with many and moving parts means extensive wear and entails difficulties with maintaining high precision. In earlier known designs, designed with outer bearings, bearing cages, strut beams, etc, high precision is required in the parts, alternatively extensive adjustments in order to obtain a paper feed perpendicularly to the chassis. The many parts in these earlier known designs make them expensive and difficult to access concerning inter alia service. Printer chassis traditionally have between six and seven parts, and they are not adapted to be used in different printer variants.
The present invention relates to a printer arrangement adapted to solve the problems mentioned above. An object of the present invention is thus to present a printer having few or variable parts.
Another object of the present invention is to obtain a printer with few force bearing points in order to minimize wear and to obtain high precision.
Yet another object of the present invention is to present a printer which is easily accessable for adjustment, exchange of parts and other service.
Accordingly, the invention relates to an arrangement for a printer, which printer comprises a chassis at which a printer mechanism as well as a feeding device comprising a print roller are mounted for printing on and feeding of a printing material. The invention is characterised in that said chassis comprises a central piece in which said roller is mounted only at one of its ends, whereby the roller""s other end is freely suspended in relation to the chassis.
The arrangement preferably comprises a feed roller mounted with one of its ends in the central piece, parallel to the printer roller. The rollers are preferably rotatably mounted in the central piece of the chassis through bearings, which bearings preferably are slide bearings.
The central piece comprises an essentially flat portion with a first side and a second side, whereby said rollers project from the first side of the flat portion of the central piece. Furthermore, said central piece comprises recesses adapted to receive said rollers from said first side of the central piece, which recesses project from the second side of the flat portion of the central piece, and in which recesses the rollers are rotatably mounted through said bearings. The second side of the second piece is adapted for mounting of a motor unit for driving said rollers to rotation via a transmission, which transmission is adapted to act on said rollers at said recesses on the second side of the central piece.
The rollers preferably have rigid roller cores, and are mounted in said recesses in the central piece to a depth of at least 40% of the total length of the roller cores. Preferably each roller is mounted in said recess with at least two bearings, longitudinally spread apart along the extension of the roller.
Said rollers are, at the free roller ends, connected by a connecting device, which connecting device preferably comprises a snap-on lock for mounting at a recess around the axis of one of the rollers, and a bearing for the other axis.
In a preferred embodiment the central piece is cast in one piece, preferably die-cast.
In an embodiment of the invention the axis of the print roller comprises, at the end which is mounted in the chassis, a D-plane portion for mounting of a transmission wheel with a stop screw, which stop screw is eccentrically placed in relation to the axis of the roller.
In an embodiment where said central piece comprises an essentially flat portion with a first and a second side, said chassis further comprises a base plate for mounting of the central piece, a cover adapted to a least partly enclose the first side of the central piece, and a hatch adapted to at least partly enclose the second side of the central piece. Parts of the chassis are common for different printer variants, and other parts of the chassis are variable for adaptation to different printer variants. Preferably the common parts comprise the central piece and the cover, and the variable parts of the chassis comprise the base plate and the hatch.
The central piece preferably comprises recesses and mounting points for different printer variants, where said recesses and mounting points preferably are intended for mounting of rollers and suspension means adapted for different types and sizes of printing material.
The central piece is preferably cast in a magnesium material. Furthermore, the base plate and the hatch are preferably provided in different widths and/or lengths.
In one embodiment the printer further comprises unwind and rewind rollers for a colour ribbon, a sensor unit, printing mechanism and feed device comprising print and feed rollers, and a motor unit for driving said unwind and rewind rollers and print and feed rollers to rotation. Furthermore the central piece comprises recesses for a suspension means for a reel of printing material. Preferably the central piece comprises several recesses for the suspension means, for adaptation to different sizes of printing material.
In a preferred embodiment of the invention, the printer is adapted for printing of labels from a paper reel, whereby a paper rewind roller is mounted with one of its ends in the central piece. Said paper rewind roller is devised with a resilient shackle with shackle legs running parallel to the paper rewind roller on opposite sides thereof. Said shackle legs are preferably arranged with inwards projecting lips, and the paper rewind roller is preferably arranged with recessed portions, in size matching said projecting lips, said shackle being extendably anchored to the paper rewind roller with a built-in spring, whereby said projecting lips can be positioned into the corresponding recessed portions in a state where the shackle is extended a distance along the paper rewind roller. In one embodiment the unwind roller for the colour ribbon is arranged with a torsion spring clutch as a drag brake.